Electronic view finder



May 2 1944- R. L. CAMPBELL ELECTRONIC VIEW, FINDER' Filed Jan. 10. 1942'INVENTOR.

ATTORNEY Patented May 2, 1944 UNl'iED STATES PATENT GFFICE ELECTRONICviEw mman Richard L. campbell, Maywood, N. .1.,assignor to Allen B. DuMont Laboratories, Inc., Passaic. N. J.. a corporation ot Delawareapplication January 10,1942, serial No. 426,921

(ci. 17a- 6.8)

Claims.

This invention relates to a viewilnder that is particularly useful inconnection with television cameras. By this invention atelevisionvcamera man can monitor the scenes or objects which are beingtransmitted while panning and focusing the pick-up camera. The imagewhich is observed in the view iinder is upright and can be madeappreciably brighter than is possible with optical means. It can be usedwith diierent sorts of television cameras now known.

In carrying out this invention the view nder is I made up as a smallmonitoring unit in compact form that is adiustably mounted upon thecamera itself in such a location that it can be conveniently adjustedand watched by the camera man as he operates the camera. Scanning andvideo signals are fed to the view iinder from the control unit that isprovided for the camera itself so that the camera man has instantly theinfomation that is being transmitted and can quickly make adjustmentsthat may be needed for obtaining better results. The view inder circuitsmay be controlled in common vwith and simultaneously with the camera.

The invention may be understood from the description in connection withthe accompanying drawing, in which:

Fig. 1 is a perspective view showing a camera and view finder mountedupon a tripod;

Fig. 2 is a block diagram illustrative of'A the invention; and v Fig. 3is a diagram of electrical connections to the camera and view nder.

In the drawing, reference character i indicates a tripod with auniversal joint 2 by means of which the camera 3 is mounted upon thetripod and can be turned to diierent positions by means of the handleThe camera is provided with a lens that is focused by means of thehandle 6 in the well known way.

The view finder 9 is connected to the camera 3 by a connection iii insuch a manner that it is swung around with the camera as the camera isturned for panning the scenes, while at the same time the view nnder canbe turned about this connection lil so as to be adjusted to diilerent vpositions in a plane parallel to the sides of the camera 3. The controlsfor the view iinder may be mounted thereon. A light shield for the viewfinder is shown at l I.

A generator for synchronizing pulses is diagrammatically indicated at i9in Fig. 2. Leads 20 and 2l for horizontal and vertical sweeps extendfrom generator i9 to the camera control unit 22, comprising camera.sweeps, view nder sweeps and main video amplifier. from which the lead23 extends to carry the output picture signals.

A lead 24 applies the video signal from the video amplifier to thesupply unit 25 for the view finder 9, and power is also supplied to thisview finder supply-unit 25 by means of the lead 26 which may lead, forexample, from a source of volt alternating current. A power and videosignal cable 2l leads from the unit 25 to the view nder 9.

A cable 30 for carrying the camera sweep signals, the camera videosignal, the view nder sweeps and other control wires is connectedbetween the unit 22 and the camera 3. Lead 32 applies the horizontal andvertical sweeps to the view nder 9 to which the lpower and the videosignal are applied by the cable 21. Sweep voltages are thus'fed from thecamera control unit 22 through the camera cable 30 and lead 32 to theview finder 9. When an iconoscope camera is used, keystoning, and theuse of circuits operating magnetically militate against using the camerasweep for the 'View iinder; thereforev the sweep circuits for the viewilnder 9 are brought directly from the cable 30 as indicated by thedotted line. The isolating stages for the view finder are ener-,gizedfrom the sweep input circuits 20, 2l of the camera control unit22, which are fed from the synchronizing generator i9. This is notnecessary with an orthicon camera since there is then no keystoning, sothat the view finder sweeps can be connected to the camera sweep lines.

The connections for the view finder are shown in more detail in Fig. 3.The horizontal sweep signal from lead 32 (Fig. 2) is applied to theoutput stage 42, from which it is applied by leads 38 to the horizontaldeection plates 39 of the cathode-ray tube 40 that is located in theview finder 9 (Fig. 1). A lve inch intensifier type cathode-ray tube hasbeen found to be very suitable as a view finder. Thevertical sweepcircuit signal, also from lead 32 (Fig. 2), is applied to the outputstage 43 (Fig. 3), from which it is applied by leads '44 to the verticaldeflection plates 45. The video signal from the camera 3 (Fig. 2) isapplied to the video amplier 46 (Fig. 3) and thence by lead 4l to thecontrol grid 48 of the tube 40 oi' the view finder 9. The other elementsof the gun structure of the tube 40 with their control circuits are ofthe well known sort and are shown somewhat diagrammatically in Fig. 3without detailed description thereof. The resistor network 49isindicated for applying Way.

'I'hls invention has been found to be practical in actual use. due,among other things. to the facts: that an intensifier type ofcathode-ray tube 40 is used so that suillcient brightness can be made toappear upon the screen, thus cnabllng one to use the view iinder 8 wherethere is very strong light such as direct strong sunlight or highintensity studio lighting; electrostatically controlled deflection isused so that straight am plifiers can be used for applying the sweep tothe cathode-ray tube in the view nder; vertical and with its attendantweight does not have to be carried by the camera; and the controls forthe video, for the sweeps, and for the cathode-ray tube are mounted onthe view finder so that they are in convenient reach of the camera man.'I'he video signal for the view finder 9 is obtained from an outputamplifier in the camera control and is fed over a coaxial cable to theview finder supply unit 25 where it can be ampliiled and from which itis fed to the view nder which has an amplifier 4B for driving thecathode-ray tube 40 in the view nder.

What is claimed is:

1. A television pick-up camera, a view finder adjustably mounted on saidc amera, a control said camera to said view finder, a lead from saidcontrol unit to said view ilnder supply unit and a lead from said viewfinder supply unit to said view ilnder.

2. A television pick-up camera, a view finder mounted on said camera, acontrol unit for said camera, means comprising leads for feedingscanning and video signals from said control unit to said view finder, asupply unit for said vicw finder, and leads connecting said supply unitto said view nder and said control unit.

3. A television pick-up camera, a view finder mounted on said camera, acontrol unit for said camera, sweep circuit connections from saidcontrol unit to said v.2.w linder, and means comprising a lead from apower supply unit and a lead from said control' unit to said supply unitand a lead from said supply unit to said view nder, to supply power andvideo signals to said view finder independently of said sweep circuitconnections.

4. A television pick-up camera, a view iinfier mounted on said camera, acontrol unit for said camera, a view finder supply unit, and means forfeeding scanning and video signals from said control unit to said viewiinder, said last named means comprising a lead from said camera to saidview finder, a lead from said control unit to said view iinder supplyuni*u and a lead from said view ilnder supply unit to said view finder,

"said view finder being provided with an intensifier .for increasing thebrightness of the picture on the screen thereof.

5. A television pick-up camera, a view iinder mounted on said camera, acontrol unit for said camera, means for feeding scanning and videosignals from said control unit. to said view finder, leads connectingsaid supply unit to said view finder and said control unit and a powersupply for said view nder independent of said camera.

RICHARD L. CAMPBELL.`

